aura-x11: Add support for xmodmap'ed pointer buttons.

ui/base/x/x11_util.cc

Index: ui/base/x/x11_util.cc
diff --git a/ui/base/x/x11_util.cc b/ui/base/x/x11_util.cc
index fed7764d7b2b3058f2bad0e780076b3d4614a8f4..690a9c770f26545d32e2c93712126c3d6d3693ac 100644
--- a/ui/base/x/x11_util.cc
+++ b/ui/base/x/x11_util.cc
@@ -18,6 +18,7 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
+#include "base/memory/singleton.h"
 #include "base/message_loop.h"
 #include "base/string_number_conversions.h"
 #include "base/string_util.h"
@@ -138,6 +139,36 @@ class XCursorCache {
   DISALLOW_COPY_AND_ASSIGN(XCursorCache);
 };
 
+// A singleton object that remembers remappings of mouse buttons.
+class XButtonMap {
+ public:
+  static XButtonMap* GetInstance() {
+    return Singleton<XButtonMap>::get();
+  }
+
+  void UpdateMapping() {
+    count_ = XGetPointerMapping(ui::GetXDisplay(), map_, arraysize(map_));
+  }
+
+  int GetMappedButton(int button) {
+    return button > 0 && button <= count_ ? map_[button - 1] : button;
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<XButtonMap>;
+
+  XButtonMap() {
+    UpdateMapping();
+  }
+
+  ~XButtonMap() {}
+
+  unsigned char map_[256];
+  int count_;
+
+  DISALLOW_COPY_AND_ASSIGN(XButtonMap);
+};
+
 }  // namespace
 
 bool XDisplayExists() {
@@ -833,6 +864,14 @@ bool IsX11WindowFullScreen(XID window) {
 #endif
 }
 
+int GetMappedButton(int button) {
+  return XButtonMap::GetInstance()->GetMappedButton(button);
+}
+
+void UpdateButtonMap() {
+  XButtonMap::GetInstance()->UpdateMapping();
+}
+
 // ----------------------------------------------------------------------------
 // These functions are declared in x11_util_internal.h because they require
 // XLib.h to be included, and it conflicts with many other headers.